Autonomous (Leadless) Intracardiac Implantable Medical Device With Releasable Base and Fastener Element

ABSTRACT

A leadless autonomous intracardiac implantable medical device having a releasable fastener system. This autonomous intracorporeal active medical device has two distinct elements connectable together and reversibly separable from one another, with a sealed capsule body ( 100 ) housing electronic circuitry ( 110 ), and a base ( 200 ) comprising a plate ( 202 ) having an outer face and an anchoring system on said outer face to anchor the base to a wall of an organ of a patient, and an inner face forming a support for the capsule body and having a fastening system to couple releasably the capsule body to the base. The capsule body comprises on its face turned towards the base at least one projection support ( 108 ) on an electrode surface for coming into contact with the wall of the organ of the patient when the capsule body is mounted on the base.

The present application claims the priority date benefit of FrenchPatent Application No. 11/55622 entitled Leadless autonomousintracardiac implant with releasable fastener element” and filed Jun.24, 2011, which is hereby incorporated by reference in its entirety.

FIELD

The present invention relates to “medical devices” as defined by theJun. 14, 1993 Directive 93/42/EEC of the Council of the EuropeanCommunities, more specifically to the “active implantable medicaldevices” as defined by the Jun. 20, 1990 Directive 90/385/EEC of theCouncil of the European Communities. This definition in particularincludes devices that continuously monitor the cardiac rhythm anddeliver if and as necessary to the heart electrical pulses for cardiacstimulation, resynchronization, cardioversion and/or defibrillation, incase of a rhythm disorder detected by the device. It also includesneurological devices and cochlear implants, as well as devices for pHmeasurement and for intracorporeal impedance measurement (such formeasuring a transpulmonary impedance or an intracardiac impedance).

The present invention relates more particularly to those devices thatinvolve autonomous implanted devices without any physical connection toa main (master) device that may be implanted (such as a generator fordelivering stimulation pulses) or not implanted (such as an externalprogrammer or device for remote monitoring of a patient). The autonomousimplanted device communicates with the main or master device using awireless communication technology.

BACKGROUND

Autonomous active implantable medical devices of the type involved inthe present invention are also known as “leadless capsules” or moresimply “capsules” to distinguish them from the electrodes or sensorsplaced at the distal end of a lead, which lead is connected at itsopposite, proximal end, to a generator and is traversed throughout itslength by one or more conductors connecting by galvanic conduction theelectrode or the sensor to that generator. Such leadless capsules are,for example, described in U.S. Pat. Publication No. 2007/0088397 A1 andWO 2007/047681 A2 (Nanostim, Inc.) or in U.S. Pat. Publication No.2006/0136004 A1 (EBR Systems, Inc.). These leadless capsules can beimplanted epicardially, i.e., fixed to the outer wall of the heart, orendocardially, i.e., fixed to the inside wall of a ventricular or atrialcavity.

The attachment to the heart wall is usually obtained by a protrudinganchoring helical screw, axially extending from the body of the capsuleand designed to penetrate the heart tissue by screwing to theimplantation site.

The leadless capsule typically includes detection/stimulation circuitryto detect (collect) depolarization potentials of the myocardium and/orto apply stimulation pulses to the implantation site (also called thestimulation site) where the capsule is located. The capsule thenincludes an appropriate electrode, which can be an active part of theanchoring screw, for electrically coupling to the mycocardium. It canalso incorporate one or more sensors for locally measuring the value ofa patient parameter, such as the oxygen level in the blood, theendocardial cardiac pressure, the acceleration of the heart wall, andthe acceleration of the patient as an indicator of activity. Of course,for the remote exchange of data, the leadless capsules incorporate atransmitter/receiver for wireless communications with another device.

It should be understood however, that the present invention is notlimited to one particular type of autonomous leadless capsule orimplanted device, and is equally applicable to any type of leadlesscapsule, regardless of its functional purpose.

The energy source is one of the major weaknesses of leadless capsulesbecause, being autonomous, it is not possible to provide energy througha lead conductor as with conventional or wired leads. Although energyharvesting devices and techniques have been proposed, to date onlyleadless capsules having battery power supply systems are trulyoperational. But given the very restrictive volume constraints, theautonomy of these batteries is limited, so that the currently availableleadless capsules have a limited life span of around six months to twoyears, and must be regularly replaced.

The replacement of a leadless capsule, in addition to the frequentreiteration of a particularly invasive surgery, causes several problems:

-   -   First, the former site of implantation, which was perhaps        optimal (especially if it was determined according to a mapping        optimization procedure) is not easily traceable;    -   Second, further trauma to the tissues are caused by the        explantation of the old device and the implantation of a new        one; and    -   Third, when the device at its end of life cannot be removed and        must be left in place, it remains as a foreign and invasive        parasitic element, which can become problematic over the years        particularly with successive device implantations.

The above problems also arise elsewhere, regardless of the cause of theleadless capsule replacement, such as for a defective electroniccircuit, replacement by a newer version device, and an elementgenerating an infection.

Moreover, the introduction to the implantation site of a leadlesscapsule of a relatively large size requires tools of appropriate size,the use of which may be traumatic for the patient.

Finally, in all the systems proposed so far, the axis of fixation of theleadless capsule (typically, the axis of the anchoring screw) is thesame as the axis of introduction of the device. For an endocardialdevice, this means that the anchoring system is at the end of theelongated cylindrical body constituting the body of the leadlesscapsule, which must necessarily be fixed perpendicularly to the heartwall. This configuration increases the invasiveness of the implantedsystem in relation to the heart function, particularly because ofgreater interference with blood flow and movement of the heart walls.

OBJECT AND SUMMARY

It is therefore an object of the present invention to provide a leadlesscapsule that, when it is to be replaced, permits:

-   -   Reusing the same implantation site;    -   Minimizing trauma to the tissues at the implantation site;    -   Removing a capsule without leaving large sutures on the        implantation site;    -   Minimizing the invasiveness during implantation, and    -   Increasing the design freedom for the shape of the capsule,        particularly by avoiding to design an implantable elongated        element, the largest dimension of which after implantation would        be perpendicular to the heart wall.

In accordance with the present invention, an autonomous implantabledevice (leadless capsule) is of the type described in US Pat.Publication No. 2002/0165589 A1 cited above, in which the leadlesscapsule implanted is separated into two distinct components, with:

-   -   A first element or “base”, dedicated to the attachment to the        heart wall, comprising a conventional anchoring structure such        as a screw, harpoon, hook or other penetrating element; and    -   A second element or “capsule body” incorporating the main active        components of the leadless capsule (e.g., the electronic        circuits and the energy source(s)),    -   wherein, the two elements are mechanically coupled together in a        reversible manner (such that the coupled elements can be        uncoupled) by a fastening system such as a clip, a screw, or a        bayonet or other reversible mount.

During the system implantation, the first element (base) is attachedfirst on the chosen stimulation site. Then, the second element (capsulebody) is inserted and secured to the base through the fastening system.

In one embodiment, the fastening system comprises projecting tabsarranged so as to define opposing contact surfaces that are used tomatch to the shape of the corresponding contact surfaces of the capsulebody. Preferably, there are two projecting tabs that are disposed at twoopposite ends of the base.

As discussed in greater detail below, such a device according to thepresent invention can be adapted to both an elongated shape (“elongatedshape” here meaning having a length that is greater than the diameter)endocardial leadless capsule, and flattened shape (a “flattened shape”here meaning having a diameter that is greater than the length)epicardial leadless capsule.

When intervention is necessary for the exchange of the capsule body(e.g., the battery is depleted, outdated system), the capsule body issimply detached from the base, and a new capsule body is installed inits place. Thus, the stimulation site is preserved and cardiac tissuesdo not suffer additional trauma due to extraction and/or re-implantationof the anchoring structure.

Moreover, such a concept significantly increases the modularity andadaptability of autonomous (leadless) implantable medical devices. Thus,for example, it is possible to define a family of capsule bodies thatcan be adapted to a standard base equipped with anchoring structure,without questioning the system implantation. Conversely, it is possibleto consider a family of bases specifically designed for implantation indifferent parts of the heart, and likely to receive the same type ofcapsule body or a same family of capsule bodies.

Broadly, a device in accordance with one embodiment of the present ofthe invention is of the type described in US Pat. Publication No.2002/0165589 A1 cited above and comprises two distinct elementsconnectable together and reversibly separable, with a sealed capsulebody housing electronic circuits, and a base comprising a plate havingan outer face with an anchoring structure that anchors the base to awall of an organ of a patient, and a inner surface forming a support forthe capsule body and having a fastening system to effect a mechanicalcoupling of the base to the capsule body. Preferably, mechanicallycoupling the base to the capsule body includes at least two projectingtabs arranged at two opposite ends of the plate, extending from theinner face of the base (away from the anchoring system), said tabs beingsubstantially parallel and defining on their opposing faces contactsurfaces matching the shape of the contact surfaces of the capsule bodyfor making a mechanical coupling.

In one embodiment, the projecting tabs may be resiliently deformable,with the contact surfaces of the base having opposing concavitiesmatching a corresponding pair of convex contact surfaces shape of thecapsule body, so as to allow a reversible mechanical coupling (i.e., afastening) of the capsule body to the base. The fastening system may usea friction fit coupling or a clip and locking detent fitment.

In one embodiment, the projecting tabs may be rigid with the contactsurfaces of the base and comprising, for example, an internal threadengaging with a corresponding complementary threaded contact surface ofthe capsule body, so as to allow reversible screwing of the capsule bodyto the base. In an alternative embodiment, the projecting tabs are rigidand comprise a curved notch engaging with counterpart coupling fingersprojecting from the capsule body, so as to allow for reversible nestingof the fingers in the notch in a bayonet mount style of fixing of thecapsule body on the base. In the latter case, the base further comprisesa resilient material positioned to bias the capsule body in thedesired'axial direction so as to allow locking of the capsule body inposition fixed to the base.

In one embodiment, the capsule body comprises a novel shaped surfacefeature whose major axis is oriented parallel to the axis of theanchoring structure, said body comprising, on its face turned towardsthe base, at least one projecting support with an electrode surfacecoming into contact with the tissues of the patient when the capsule ismounted on the base. A side wall of the projecting support can then beprovided, for coming into contact with an edge of the plate so as toensure axial blocking of any rotation of the capsule body relatively tothe base. The anchoring structure axis is preferably oriented normal tothe surface of the patient's tissue to which the base is anchored.

In one embodiment, the capsule body comprises electrodes coupled tocontacts arranged on the inside of the base, these contacts beingthemselves connected to electrodes formed on the outer part of the basefor coming into contact with the wall of the patient's organ to whichthe base anchoring system is affixed.

In one embodiment, the capsule body comprises, on its face opposite tothat turned towards the base, a cover bearing a conductive surfaceforming a ground electrode, for coming into contact with a bodily fluidof the organ of the patient when the capsule body is mounted on thebase.

One embodiment of the present invention concerns an implementation inwhich the capsule body comprises at least two elements that may bestacked or coupled together, preferably releasably coupled, such that afirst capsule body has on its opposite face to that turned towards thebase, a fastening system for fixing to a separable second capsulewithout separation of the first capsule body from the base. Thefastening system used to form the stack of the two elements may be oneof the types of fastening systems described herein for fastening thecapsule body to the base. In this embodiment, the leadless capsule isformed by stacking of the first and second sealed capsule bodies and thebase using such fastening systems. In a preferred embodiment, the firstcapsule, body contains the active components, and the second capsulebody may include a power supply (e.g., a battery) for powering theelectronic circuits housed in the first capsule body. In thisembodiment, electrical contacts through the first and second capsulebodies are provided to electrically connect the power supply in thesecond capsule body to the electronic circuits in the first capsule bodywhen the two are fastened together.

Another embodiment of the present invention concerns a capsule body witha novel shaped surface the axis of which is oriented perpendicularly tothe axis of the anchoring system, and wherein the capsule bodycomprises, on at least one region of axial end, an annular ring with anelectrode surface for coming into contact with the tissues of thepatient when the capsule body is mounted on the base.

In all cases, the capsule body and/or the base can be advantageouslyprovided with radiopaque markers to facilitate later extraction of thecapsule body and then of setting up of a new capsule body fastened tothe base, which remains implanted in situ.

DRAWINGS

Further features, characteristics and advantages of the presentinvention will become apparent to a person of ordinary skill in the artfrom the following detailed description of preferred embodiments of thepresent invention, made with reference to the drawings annexed, in whichlike reference characters refer to like elements, and in which:

FIG. 1 schematically illustrates a set of medical devices, includingleadless implantable medical devices, implanted within a patient's body;

FIG. 2 schematically illustrates more precisely how to implant theseleadless implantable devices on the inner or outer myocardium wall;

FIG. 3 is a functional schematic block diagram showing the variousstages constituting of a leadless capsule;

FIGS. 4 a to 4 e illustrate a first embodiment of a leadless capsuleaccording to the present invention, for an epicardial capsule with clipfastening of the cap to the base;

FIGS. 5 a and 5 b illustrate a second embodiment of a leadless capsuleaccording to the present invention, for an endocardial capsule with clipfastening of the capsule to the base;

FIGS. 6 a and 6 b illustrate a third embodiment of a leadless capsuleaccording to the present invention, for a capsule body with epicardialfixation by screwing of the capsule body onto the base; and

FIGS. 7 a to 7 c illustrate a fourth embodiment of a leadless capsuleaccording to the present invention, for a capsule with epicardialfixation by a bayonet system fixing the capsule body to the base.

DETAILED DESCRIPTION

Various embodiments of the present invention will now be described withreference to the drawings FIGS. 1-7 c. In FIG. 1 a set of medicaldevices implanted in the body of a patient is illustrated. The patientis implanted for example with a device 10 such as an implantabledefibrillator/pacemaker/resynchronizer or a subcutaneous defibrillatoror a long-term recorder. Device 10 is deemed the master device 10 of anetwork comprising a plurality of slave devices 12 to 18 with which itcommunicates intracorporally through human body communication (“HBC”).These devices may include intracardiac devices 12 or epicardial devices14 (or both) directly implanted on the patient's heart, other devices 16such as myopotential sensors or neurological stimulation devices, andpossibly an external device 18 disposed, for example, an armband andprovided with electrodes in contact with the patient's skin. Masterdevice 10 can also be used as a gateway to the outside world tocommunicate with an external device 20, such as a programmer device or adevice for remote transmission of data, with which they can communicate,for example, by RF telemetry.

Each of master and slave devices 10-18 is provided with at least onepair of electrodes that are in direct contact with body tissues forimplanted devices, or in contact with the skin in the use of an externaldevice 18.

With reference to FIG. 2, examples of leadless capsules implanted eitheron the inside part of the myocardium, in an atrial or ventricular cavity(endocardial implants 12) or on an outer wall of the same myocardium(epicardial implants 14) are shown. These devices are attached to theheart wall by means of a projecting anchoring screw for penetrating incardiac tissue by screwing at the implant site. The screw can be apassive screw, only used for anchoring of the base, or an active screw,to collect the depolarization signals propagating in the tissues of themyocardium and/or to locally deliver stimulation pulses to theimplantation site.

FIG. 3 schematically illustrates the internal electronic circuits ofcapsules 12 or 14. In this embodiment, each capsule includes a pair ofelectrodes 22, 24 connected to a stimulation pulse generator circuit 26(for an active implantable medical device incorporating this function)and/or a detection circuit 28 for the collection of depolarizationpotentials collected between the electrodes 22 and 24. A centralprocessor unit circuit 30 includes all of the circuitry to control thevarious functions of the implant, e.g., the storage of the collectedsignals. It comprises a microcontroller or microprocessor and anoscillator generating the clock signals needed for operating themicrocontroller and communication. It may also contain an analog/digitalconverter and a digital storage memory. The capsule may also be providedwith a sensor 32 such as an acceleration sensor, a pressure sensor, anhemodynamic sensor, a temperature sensor, an oxygen saturation sensor,etc.

The leadless capsule includes a power supply 34 which may be a smallbattery and/or an energy harvester circuit supplying all the electroniccircuits via a power management stage 36. The electrodes 22 and 24 arealso connected to a modulator/demodulator circuit 38 coupled to thecentral processor unit circuit 30 and emitting and/or receiving pulsesused for wireless HBC communication. Thus, according to whether thestimulation circuit (module 26) and the detection circuit (module 28)are present or not, the electrodes 22, 24 can provide a single, doubleor triple function, namely: stimulation and/or detection of cardiacpotentials (if applicable) and/or transmission of data monitored by thesensor 32 (if applicable) and emission/reception for the HBCcommunication (in any case).

Characteristically of the invention, and as illustrated in FIGS. 4-7,capsule 12 or 14 includes a capsule body 100 mounted on a base 200 by areversible coupling fastening system.

FIGS. 4 a to 4 e illustrate a first embodiment of the present invention,for an epicardial capsule with clip fastening of capsule body 100 tobase 200. In this embodiment, capsule body 100 comprises a flattenedshape cylindrical body, typically of a few millimeters thick and from 8to 12 mm in diameter, closed by a lid 104 at its upper part (that is tosay on the side opposite to the wall on which the capsule body 100 isintended to be fixed to base 200).

The exterior of capsule body 100 can be made of titanium, according to aconventional stamping technology of a thin sheet of implantable titaniumthat complies with ISO 5832-2, or of any other biocompatible metal.

Alternatively, capsule 100 may be made of a biocompatible plasticmaterial, by molding or any other technique to encapsulate the internalcomponents housed capsule body 100. The biocompatible plastic can be forexample, a Tecothane (registered trademark), which is a thermoplasticpolyurethane based on a medical grade aromatic polyether and which maybe radiopaque.

On its lower surface 106 (see especially FIG. 4 d) capsule body 100comprises two protrusions 108, including the surfaces intended to comeinto contact with heart tissue, which includes electrodes 22, 24 forsensing/pacing/defibrillation. These electrodes have a surface area offrom a few square millimeters to several tens of square millimeters.

As shown in FIG. 4 e, capsule body 100 houses a circuit 110 containingthe active elements, the power supply battery, the sensors, and theconnections to the electrodes. Circuit 110 is housed in body 102 of thecapsule 14 which is sealed by lid 104, for example, by welding tocylindrical body 102. The central part of lid 104 may optionally includea conductive surface 112 forming a ground electrode, isolated from therest of body 102 by a peripheral ring 114 made of an insulatingmaterial.

Base 200 includes a plate 202 on which the bottom surface 106 of body102 is supported. The underside of plate 202 bears the anchoringstructure to anchor base 200 to the patient's cardiac wall, which inthis embodiment is a helical screw 204 of 2 to 3 mm in diameter.

On the opposite side, that is to say the side facing capsule body 100,plate 202 is provided with a generally rectangular shape having a majoraxis and at each of its ends a projecting tab 206. In this embodiment,projecting tab 206 are elastically deformable. The plate 202 andprojecting tabs 206 are advantageously made of medical grade Tecothane(registered trademark). Projecting tabs 206 extend upwardly in asubstantially parallel direction and have in their opposing faces aslight concavity 208, matching and in part overlapping the shape of thecombined peripheral surface, preferably slightly convex, of body 102, soas to ensure the retention of capsule body 100 by clipping body 102between the two elastically deformable projecting tabs 206.

Advantageously, as shown in FIG. 4 c which discloses the entire capsulebody 100/base 200 in a pacing configuration, protrusions 108 of capsulebody 100, which carry the respective electrodes 22 and 24, are fit withno clearance or a very slight clearance against flanges 210 of thecentral portion of plate 202, thereby rotationally locking capsule body100 relatively to base 200 and preventing any change in the stimulationzones, that is to say zones of the heart wall located in contact witheach of the two electrodes 22 and 24. It should be noted that, forcontact with the heart to be effective, the thickness of projectingelements 108 must be greater than the thickness of the central part ofplate 202.

In an alternative embodiment, the stimulation (and/or detection)electrodes in contact with the tissues to be stimulated are formed onbase 200 and not on capsule body 100. In this case, body 102 of capsulebody 100 is provided with electrodes coupled to contacts arranged on theinside of base 200, which contacts are in turn connected to electrodeson the outside of base 200, in contact with patient tissues. Thisembodiment makes possible in particular stimulation via the anchoringstructure of the base fixed to the tissues, e.g. by anchoring screw 204.

According to another aspect of the invention, base 200 and/or capsulebody 100 may be provided with radiopaque markers to facilitate futureoperations of extraction of capsule body 100 and then of setting up andfastening a new capsule body 100 on base 200, which base 200 is leftimplanted in situ.

FIGS. 5 a and 5 b illustrate a second embodiment of the autonomousactive implantable device of the present invention, for an endocardialcapsule with clip fastening the capsule body to the base. In thisembodiment, capsule body 100 is in the form of an elongated member withan elongated body terminated with two domed ends 118. The capsule bodyhas a longitudinal dimension of the order of 10 mm, and a maximumdiameter of a few millimeters. Note that in this configuration, capsulebody 100 is disposed with its longitudinal axis oriented in a directionD1 substantially parallel to the cardiac wall, that is to sayperpendicular to the axis D2 of the anchoring system 204 of base200—unlike the previous embodiment illustrated in FIGS. 4 a-4 e, whereinthe two axes are essentially aligned and combined.

Base 200 comprises two elastic tabs 214 defining on their inner sides, aconcave surface 216, which is a complementary counterpart to outersurface 116 of capsule body 100. The length of tabs 214 is such thatends 220 thereof are beyond the diameter region of capsule body 100, soas to ensure retention in place thereof after capsule body 100 has beenfitted into base 200, again with a snap-fit fastening connection.

Capsule body 100 is preferably provided on both sides of base 200 withtwo annular rings 120, arranged near ends 118 in the form of an ogiveand carrying electrodes 22, 24 in the form of conductive surfaces overthe entire periphery of rings 120. This configuration allows contactwith heart tissue regardless of the method by which capsule body 100,which has symmetry of revolution about the axis D1, has been fitted ontobase 200. It also provides a relatively large spacing between electrodes22 and 24, in favor of more effective stimulation.

It should be understood that the small diameter (e.g., a fewmillimeters) of capsule body 100 allows for a very atraumaticintroduction to the implantation site. The capsule body 100 is thenturned a quarter turn at the time of fitting onto base 200, so as toorient it with the axis D1 of the capsule perpendicular to the axis D2of the base and of the anchoring system screw.

In an alternative embodiment (not illustrated), the system has several,typically two, bases set side by side on the heart wall and onto which asingle capsule body is fit. The device is thus attached to the wall atseveral, typically two, locations, which increases the contact surfaceand provides greater freedom as regards the choice of the stimulationsites, and a better mechanical resistance due to the absence any ofpreferred rotation or bending axis.

FIGS. 6 a and 6 b illustrate a third embodiment of the leadless capsulein accordance with the present invention, for a capsule with epicardialfixation by screwing the capsule body onto the base. In thisconfiguration, projecting tabs 206 of base 200 are provided on theirinner faces with a thread 224 fitting with a complementary thread 122formed on the counterpart outer surface body 102. The setup of capsulebody 100 on base 200 is then performed by screwing. Lid 104 of thecapsule body is advantageously provided with recesses 124 for engaging atool to effect rotation of the capsule body.

In FIG. 6 b, an embodiment in which the autonomous active implantablemedical implant can include a plurality of stacked capsule bodies suchas 102, 102′ is illustrated: body 102 is reversibly coupled to the baseby a fastening system as described above, and encloses for example allthe electronic circuits. On the other hand, body 102′ is superimposed onand secured to body 102 using a second fastening system, and containsthe power supply. In this way, body 102′ can be replaced while leavingin place body 102 mounted on base 200 and base 200 anchored to thepatient's tissue. A suitable electrical connection is provide toelectrically couple the power supply to the electronic circuits whenbodies 102 and 102′ are fastened together in a stack.

FIGS. 7 a to 7 c illustrate a fourth embodiment of the autonomous activeimplantable medical device of the present invention, for an epicardialcapsule with fixation to the base by a bayonet mounting system. In thisconfiguration, projecting tabs 206 are rigid and each includes a curvedguiding notch 226, 228 having a “J”-like channel dimensioned tocooperate with a coupling finger 126 formed on and projecting from aside wall of capsule body 100. The implementation is in the same manneras a conventional bayonet coupling for an electric lamp base and bulb orcamera lens and body system, by a “pushed-turned” movement. Theretention of for examples two fingers 126 in respective notches 226, 228is provided by elastic material elements 230 formed on plate 202. Theseelastic elements 230 ensure that, once the movement of introduction ofcapsule body 100 into base 200 is completed, coupling fingers 126 arebiased securely in the bottom 228 of the curved guiding notch 226.

In this embodiment, the stimulation electrodes 22, 24 are carried byprojecting elements 128 formed on the lower surface of the capsule 100body and intended to come into contact with heart tissue once thecapsule body 100 is fitted on base 200.

One skilled in the art will appreciate that the present invention can bepracticed by other than the embodiments disclosed herein, which areprovided for purposes of illustration and explanation and not oflimitation.

1. An intracorporeal autonomous active medical device (12, 14),comprising: A sealed capsule body (100) having an external shape andcontaining therein electronic circuitry (110), and A base (200)comprising a plate (202) having two opposing ends, an outer face and aninner face, an anchoring structure connected to said outer face toanchor said base to a wall of an organ of a patient, said inner facecomprising a support for the capsule body and a fastening system tomechanically fasten in a reversible manner said base to said capsulebody; Wherein the fastening system comprises at least two projectingtabs (206) disposed in opposition at said two opposing ends of theplate, said projecting tabs being substantially parallel and havingopposing faces, said opposing faces defining contact surfaces matchingthe shape of a corresponding surface of the capsule body for mechanicalfastening thereto.
 2. The device of claim 1, wherein the correspondingsurface of the capsule body shape further comprises at least two convexcontact surfaces, the projecting tabs (206) are elastically deformable,and the protecting tabs contact surfaces further comprise opposingconcavities (208) matching the corresponding convex contact surfaces ofthe capsule body, for a reversible fastening by clipping of the capsulebody on the base.
 3. The device of claim 1, wherein the correspondingcapsule body shape further comprises at least a first threaded surface,the projecting tabs (206) are rigid tabs, and the opposing contactsurfaces of the projecting tabs further comprise threaded surfacescorresponding to and threadably engageable with said first threadedsurface for reversible fastening by screwing of the capsule body to thebase.
 4. The device of claim 1, wherein the corresponding capsule bodyshape further comprises at least two coupling fingers and the projectingtabs are rigid and comprise curved notches (226, 228) for engaging withsaid coupling fingers (126), for a bayonet mount reversible fastening ofthe capsule body on the base, the base further comprising a resilientmaterial, said resilient material biasing the capsule body in the axialdirection for locking the capsule body coupling fingers in the curvednotches and the capsule body fastened to the base.
 5. The device ofclaim 1, wherein the base further comprises at least one electrode onthe outer face for contacting the wall of the patient's organ, thecapsule body (102) further comprises an electrode and the base furthercomprises an electrical contact on said inner face, said electricalcontacts being connected to at least one electrode formed on the outerface of the base for contacting the wall of the patient's organ, andwherein said capsule body electrodes are connected to said baseelectrical contacts when said capsule body is fastened to said base. 6.The device of claim 1, wherein the anchoring structure has an axis thatis normal to the wall of the patients' organ and the correspondingcapsule body (102) shape further comprises an elongated shape having amajor axis oriented parallel to the axis of the anchoring structure; andwherein the capsule body further comprises at least one supportprojection (108, 128) carrying an electrode surface (22, 24) disposed tocontact the tissues of the patient when the capsule body is fastened tothe base.
 7. The device of claim 6, wherein the base plate furthercomprises a flange and the capsule body support projection (108) furthercomprises a side wall positioned to contact said flange (210) of theplate and to lock against axial rotation of the capsule body relativelyto the base.
 8. The device of claim 6, wherein the capsule body (102)comprises, on its face opposite to that facing the base, a lid (104)having a conductive surface (112) forming a ground electrode, for comingin contact with a patient's body fluid when the capsule body is fastenedon the base.
 9. The device of claim 6, wherein the capsule body (112)comprises, on its face opposite to that facing towards the base, meansfor fastening an additional element (102′) separable from the capsulebody without separation of the capsule body from the base, the body(102) and the additional element (102′) thereby forming a stack (102,102′).
 10. The device of claim 9, wherein the additional element (102′)houses a power supply for the electronic circuits housed in the capsulebody (102).
 11. The device of claim 1, wherein the anchoring systemfurther comprises an axis (D2) normal to the wall of the patient tissueand the corresponding capsule body shape further comprises an axis (D1)that is oriented perpendicularly to the axis (D2) of the anchoringstructure, and wherein the capsule body comprises an elongated shapehaving at least one axial end region, and an annular ring positioned atsaid axial end, having an electrode surface (22, 24) for coming intocontact with the tissues of the patient when the capsule body isfastened to the base.
 12. The device of claim 1, wherein at least one ofthe capsule body (100) and the base (200) further comprises aradio-opaque marker.
 13. The device of claim 6 wherein the capsule bodyfurther comprises a first body and a second body, wherein the first bodycontains said corresponding shape fastening the first body to saidprojecting tabs of said base, and wherein said first and second bodiesare mechanically fastened together in a reversible manner and can beuncoupled without uncoupling said first body from said base.
 14. Thedevice of claim 13 wherein the first body contains said electroniccircuitry and the second body contains a power supply, wherein saidpower supply is electrically connected to energize said electroniccircuitry when said first and second bodies are mechanically fastenedtogether in a stack.